RHSA-2015:2154 - Security Advisory

Topic

Updated krb5 packages that fix two security issues, several bugs, and add
various enhancements are now available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having Moderate security
impact. Common Vulnerability Scoring System (CVSS) base scores, which give
detailed severity ratings, are available for each vulnerability from the
CVE links in the References section.

Description

Kerberos is a network authentication system, which can improve the security
of your network by eliminating the insecure practice of sending passwords
over the network in unencrypted form. It allows clients and servers to
authenticate to each other with the help of a trusted third party, the
Kerberos key distribution center (KDC).

It was found that the krb5_read_message() function of MIT Kerberos did not
correctly sanitize input, and could create invalid krb5_data objects.
A remote, unauthenticated attacker could use this flaw to crash a Kerberos
child process via a specially crafted request. (CVE-2014-5355)

A flaw was found in the OTP kdcpreauth module of MIT kerberos.
An unauthenticated remote attacker could use this flaw to bypass the
requires_preauth flag on a client principal and obtain a ciphertext
encrypted in the principal's long-term key. This ciphertext could be used
to conduct an off-line dictionary attack against the user's password.
(CVE-2015-2694)

The krb5 packages have been upgraded to upstream version 1.13.2, which
provides a number of bug fixes and enhancements over the previous version.
(BZ#1203889)

Notably, this update fixes the following bugs:

• Previously, the RADIUS support (libkrad) in krb5 was sending krb5

authentication for Transmission Control Protocol (TCP) transports multiple
times, accidentally using a code path intended to be used only for
unreliable transport types, for example User Datagram Protocol (UDP)
transports. A patch that fixes the problem by disabling manual retries for
reliable transports, such as TCP, has been applied, and the correct code
path is now used in this situation. (BZ#1251586)

• Attempts to use Kerberos single sign-on (SSO) to access SAP NetWeaver

systems sometimes failed. The SAP NetWeaver developer trace displayed the
following error message:

No credentials were supplied, or the credentials were
unavailable or inaccessible
Unable to establish the security context

Querying SSO credential lifetime has been modified to trigger credential
acquisition, thus preventing the error from occurring. Now, the user can
successfully use Kerberos SSO for accessing SAP NetWeaver systems.
(BZ#1252454)

All krb5 users are advised to upgrade to these updated packages, which
correct these issues and add these enhancements.

Solution

Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux Server 7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.5 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.4 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.3 x86_64
• Red Hat Enterprise Linux Server - AUS 7.7 x86_64
• Red Hat Enterprise Linux Server - AUS 7.4 x86_64
• Red Hat Enterprise Linux Server - AUS 7.3 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support 7 x86_64
• Red Hat Enterprise Linux Workstation 7 x86_64
• Red Hat Enterprise Linux Desktop 7 x86_64
• Red Hat Enterprise Linux for IBM z Systems 7 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.7 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.6 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.5 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.4 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.3 s390x
• Red Hat Enterprise Linux for Power, big endian 7 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.7 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.6 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.5 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.4 ppc64
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.3 ppc64
• Red Hat Enterprise Linux for Scientific Computing 7 x86_64
• Red Hat Enterprise Linux Server from RHUI 7 x86_64
• Red Hat Enterprise Linux Server - AUS 7.6 x86_64
• Red Hat Enterprise Linux for Power, little endian 7 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.7 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.6 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.5 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.4 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.3 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.2 ppc64le
• Red Hat Enterprise Linux Server - TUS 7.7 x86_64
• Red Hat Enterprise Linux Server - TUS 7.6 x86_64
• Red Hat Enterprise Linux Server - TUS 7.3 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support (for IBM z Systems) 7 s390x
• Red Hat Enterprise Linux EUS Compute Node 7.7 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.6 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.5 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.4 x86_64
• Red Hat Enterprise Linux EUS Compute Node 7.3 x86_64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.7 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.6 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.4 ppc64le
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 7.3 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.7 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.6 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.4 x86_64
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 7.3 x86_64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support for IBM Power, big endian 7 ppc64
• Red Hat Enterprise Linux Server - Extended Life Cycle Support for IBM Power, little endian 7 ppc64le

Fixes

• BZ - 1156144 - krb5 upstream test t_kdb.py failure
• BZ - 1163402 - kdb5_ldap_util view_policy does not shows ticket flags on s390x and ppc64
• BZ - 1164304 - Upstream unit tests loads the installed shared libraries instead the ones from the build
• BZ - 1185770 - Missing upstream test in krb5-1.12.2: src/tests/gssapi/t_invalid.c
• BZ - 1193939 - CVE-2014-5355 krb5: unauthenticated denial of service in recvauth_common() and others
• BZ - 1203889 - RFE: Rebase krb5 in RHEL7.2 to krb5 1.13 (krb1.13.2) ...
• BZ - 1216133 - CVE-2015-2694 krb5: issues in OTP and PKINIT kdcpreauth modules leading to requires_preauth bypass
• BZ - 1222903 - [SELinux] AVC denials may appear when kadmind starts
• BZ - 1247608 - [RFE] Add support for multi-hop preauth mechs via |KDC_ERR_MORE_PREAUTH_DATA_REQUIRED| for RFC 6113 ("A Generalized Framework for Kerberos Pre-Authentication")
• BZ - 1247751 - krb5-config returns wrong -specs path
• BZ - 1247761 - RFE: Minor krb5 spec file cleanup and sync with recent Fedora 22/23 changes
• BZ - 1250154 - [s390x, ppc64, ppc64le]: kadmind does not accept ACL if kadm5.acl does not end with EOL
• BZ - 1251586 - KDC sends multiple requests to ipa-otpd for the same authentication
• BZ - 1259846 - KDC does not return proper client principal for client referrals

CVEs

• CVE-2014-5355
• CVE-2015-2694

References

• http://www.redhat.com/security/updates/classification/#normal